Method and system for limiting water boiler heat input

ABSTRACT

A method to control the heat input into a boiler utilizing the boiler return temperature to minimize the heat input and maximize the efficiency of the boiler.

BACKGROUND

1. Technical Field

The disclosed subject matter generally relates to a method and systemfor controlling and minimizing the heat input into a water boiler, whilemaintaining the same heat output. Particularly, the disclosed subjectmatter relates to a method and system that improves the overall thermalefficiency of a water boiler.

Heat Input relates to the amount of fuel oil, natural gas, electricity,or other energy that is needed to produce a given amount of Heat Input,commonly measure in BTUs.

Heat Output refers to the usable heat produced, by a device such as awater boiler, from this Heat Input, also measure in BTUs.

Minimizing the Heat Input while maintaining a given Heat Output improvesthe efficiency of the water boiler.

SUMMARY

In one aspect this invention provides a method to improve the efficiencyof a water boiler. The method allows the system to limit the heat inputof the water boiler while maintaining the same heat output of theboiler. The method accomplishes this by monitoring the returntemperature of the heating loop to limit the heat input based on thereturn temperature.

In another aspect this invention provides a method to adjust theefficiency based on the heat demand required.

These aspects, as well as others, are described in more detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a Typical Single Zone Heating System; and

FIG. 2 depicts a New Single Zone Heating System according to oneembodiment disclosed herein; and

FIG. 3 is a flowchart illustrating the Control Logic to maximize theefficiency of the boiler.

DETAILED DESCRIPTION

Although the disclosed subject matter has been shown and described withrespect to the detailed embodiments thereof, it will be understood bythose of skill in the art that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the disclosed subject matter. In addition,modifications may be made to adapt a particular situation or material tothe teachings of the subject matter without departing from the essentialscope thereof. Therefore, it is intended that the disclosed subjectmatter not be limited to the particular embodiments disclosed in theabove detailed description, but that the disclosed subject matter willinclude all embodiments falling within the scope of the disclosure.

FIG. 1 illustrates a Typical Single Zone Heating System (10). A boiler(20) converts heat input to heat output. The thermostat (22) in theheated area turns on to indicate a heat demand. Through the furnacecontroller (23), the circulator (24) activates and circulates waterthrough the heating loop (25). When the circulator is active, the burner(26) activates to heat the water. The boiler temperature is maintainedwith the controller (23) on the boiler. This controller turns the burner(26) on when the circulator (24) is on, and will remain on unless anadjustable high temperature set point is reached or the circulator turnsoff. If the high temperature is reached the burner remains off until thewater temperature drops to specific lower temperature set point, anun-adjustable difference from the high temperature set point. Thecurrent method allows the water temperature to continue to rise even ifthe Heat Loop (25) is at a high temperature and the heat demand is aboutto be satisfied.

Some water boilers integrate domestic hot water (tap water), where thewater boiler maintains a temperature range constantly for the heatexchanger in the water boiler; these boilers have both a high and lowsettable temperature limit.

FIG. 2 illustrates the New Single Zone Heating system (10). This systemhas the same components as shown in FIG. 1, with the addition of anadjustable temperature switch (27), and a relay (28). This systemmonitors the return temperature of the loop with an adjustabletemperature switch (27), with a relay (28) to limit the burner's ontime, based on the return temperature. This allows the Heat Loop's (25)return water temperature to rise and the relay to shut off the burnerbased on the return temperature. Enabling the water in the heating loopto cool to a lower temperature as the heat demand is satisfied. Thelower the water temperature when the heat demand is satisfied, the moreefficient the heating cycle becomes.

By adjusting the maximum return temperature an effective cycle can bemaintained. This can be applied to single zone or multiple zone systems,and water boilers with and without domestic hot water heat exchangers.

In a multiple zone system, if another zone activates during the coolingportion of the cycle, the cool water from the activated zone decreasesthe return temperature and the burner reactivates until the maximum isreached.

This method requires the addition thermal switch (27, FIG. 2) or thermalsensor and a relay (28, FIG. 2) to turn off the burner, no changesbeyond the boiler are required. This makes retrofit of existing boilerseasy as well as addition to new installations.

FIG. 3 defines the Control Logic of the new system. When the thermostatin the heated area calls for heat (110) it signals the controller toturn on the circulator to turn on (120). As the water flows through theHeating loop, the return temperature is monitored (130) by the thermalswitch (27, FIG. 2). If the return temperature is below the settemperature, the relay (28, FIG. 2) remains in its' normally closedposition. Once the water temperature reaches the set temperature therelay (28, FIG. 2) is energized to its' open state (140) and the burnershuts off. The burner will remain off until the heat demand is satisfied(the thermostat shuts off the circulator), or the return temperaturefalls below the set temperature (150).

As the heat output required to satisfy the heat demand changes, due toexternal temperature, the set points may be increased for colderweather, or decreased for warmer weather.

For unusual heat demands, an extreme cold day, a timer can be added tokeep the burner on when long cycles are encountered. This bypasses thethermal switch.

This method may be applied to multiple zone system.

In a multiple zone system, if an additional zone is activated while therelay is in the open position, the cooler water from the activated zonedecreases the return temperature and returns the relay (28) shown inFIG. 2, to the closed (burner on) position (160).

1. This method reduces the heat input into a water boiler and increasesthe thermal efficiency of the water boiler.
 2. This method reduces thefuel consumption of the water boiler.
 3. This method allows adjustmentof the boiler to maintain the thermal efficiency as the heat demandchanges due to external temperature.
 4. This method reduces the averagemaximum temperature of the water boiler.
 5. This method reduces themaintenance and repair cost of the boiler due to less burner time andlower Maximum Temperature.